Process of preparing printing-plates.



A. R. BOURGES. PROCESS OF PREPARING PRINTING PLATES.

I APPLICATION FILED SEPT. 8. 1914. 1,237,238. Patented Aug. 14,1917.

ALBERT IR. BOURGES,

FFKQEQ ILLINOIS.

OF CHICAGO,

PROCESS OF PREPARING PRINTING-PLATES.

Application filed September 8, 1914.

To all whom it may concern:

Be it known that I, ALBERT R. BOURGES, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Processes of PreparingPrinting-Plates, of which the following is a specification.

This invention relates to improvements in printing plates and processesof preparing the same, and it has for its salient objects to provide anoriginal plate of such character that when used as a master-plate, fromwhich to reproduce electro-types, nickeltypes, lead molds, or otherprinting plates, the latter will come from the mold with propermake-ready or tone characteristlcs embodied in them; to provide aprocess by which an original or master plate, made as usual in otherrespects, can be re-formed by simple treatment, readily within the rangeof such skill as is conveniently attainable in the art, so as to embodyin itself the desired characteristics requisite to impart to the finalprinting plates made from this master plate self contained make readycharacteristics; to provide a process or method of making and preparingprinting plates which enables the progress of the make-ready treatmentto which the original or master plate is subjected susceptible of testfrom time to time, to the end that the precise desired result may besecured without guess-work; to provide a process of mak ing printingplates which is extremely eccnomical in that the special make-ready isperformed upon the original or master plate only, and any desired numberof electrotypes or other reproductions may be made from such original,each having the same make-ready characteristics; to provide a processwhich greatly minimizes the chances of mistakes in setting up the formsand securing the exact desired results wanted in that it eliminates thepossibilities of mistakes due to misplaced make-ready; to pro videprinting plates and a process of making the same which produces platessuitable for use for most, if not all, of the modern printing presses;to provide printing plates of a character especially valuable and ad--vantageous for use in multi-color printing, and particularly when suchmulticolor printing is done on multi form presses which impart theseveral color impressions to the Specification of Letters Patent.

Patented A11 14, 1917.

Serial No. 860,573.

sheet of paper as it passes through the press a single time; and ingeneral, to produce printing plates embodying numerous novelcharacteristics having many advantages over those heretofore in use.

In the accompanying drawing Figure 1 is a representation of animpression proof of a half-tone plate which has been subjected to myimproved treatment;

Fig. 2 is a rear View of the plate from which the impression of Fig. 1was made, showing the different steps or treatments to which the back ofsaid plate has been subjected;

Fig. 3 is a cross sectional view of the plate on line 38 of Fig. 2 afterit has been etched and tooled but before re-forming by pressure;depressions and elevations being greatly exaggerated;

Fig. 4 is another view on the same line of section but of anelectrotype, nickeltype, or other printing plate made from the masterplate; depressions and elevations being greatly exaggerated.

Two types of make-ready have heretofore been commonly employed, viz:first, building up the make-ready out of superposed sheets of paper andinstalling the same under the tympan sheets in register with theprinting plate, the latter remaining unmodified from its original fiatface form, and, secondly, incorporating the make-ready with the printingplate itself either by backing up the printing plate with paper sheetmake-ready or by so treating the plate as to vary its thickness and thusvary the printing pressure over different parts of its area.

Somewhat recently a form of the last mentioned method or process hasbeen brought out, known as the McKee process (disclosed in Patent No.857,581), in which process the original or master plate is made in theusual way, and from this original electrotypes or other printing platesare prepared as usual, and then these electrotypes or otherreproductions are specifically treat ed t incorporate in them themake-ready character in accordance with the following general plan Eachelectrotype or other final printing plate is depressed or-indented as toits face by means of pressure applied through a make-ready, which isbuilt up the reverse of what is wanted in the final face contour of theplate. That is to say, where the heaviest pressure and shades are wantedthe maker-early is thinnest, and over those areas where the lightestimpressions or blanks are wanted, the make-ready is thickest. The reliefareas at the back of the plate are planed off so as to give the plate auni-' form plane back, while its face retains the modified contour intowhich it has been pressed.

My invention is somewhat analogous to the said McKee process and platesproduced therefrom in that my process also results in printing plates ofvarying thickness and of self-contained make-ready character. But myinvention differs radically from the said McKee process in theserespects, among others: First, I perform all the make-ready treatmentupon the master plate, and, secondly, the process which I employ inreshaping the original or master plate is very different from thatemployed in the McKee process; is susceptible of finer gradations as toresults, eliminates the necessity of special tools or machines and iscapable of securing many advantages.

In practising my invention in a preferred way, I start with an originalcopper or other metal plate, which has had its printing or impressionface produced by any'of the usual processes and I prefer that thisplate, if of copper, be not thicker than 16 gage thickness; this being ausual thickness. A some what thinner gage responds more readily to mytreatment. In the making of this original plate care is to'be taken inorder to insure that its back remains smooth and protected from beingpitted by the etching to which" it is subjected. This original havingbeen properly cleaned, I first make a few impressions therefrom on anysuitable paper and with any ordinary ink, to determine itsprimalprinting condition, and also in order that I may have at least oneprintedv impression sheet for the use hereinafter described.

I next proceed to place on the back side of the plate guide orimpression marks whereby I may selectively treat different areasthereof, and I prefer to proceed as now about to be described, thoughvarious other ways will occur to those skilled in the art fortransferring such working lay-out.

While one of these impression sheets is still in printing contact withthe face of the original plate, I suitably mark its margins or trim themoff so that I may transfer it to the back of the plate and place it inexact reverse register, 2'. 6., in exact opposition to the correspondingparts on the face of the plate. I carefully inspect this printedimpression and determine those areas which are to be tone-modified inthe plate. I place next to the back ofthe plate a sheet of ordinarycarbon transfer paper, and then mount the register sheet over the carbonsheet with theimpression side out and in correct register as described.I next proceed to outline with a suitable pencil or stylus those areaswhich are to be printed with the strongest shading or tones andtherefore which are to be held highest in the final printing plate,including also, if desired, any burnished places, which are naturallylow, and similarly outline those areas which are to be treated toproduce medium shades or tints, and likewise outline those areas whichare to be of lightest shades and those which are not to print at all.Ihese outline marks are, of course, impressed on the back of the platethrough the carbon. I now remove the impression sheet and carbon andproceed to etch the back of the plate properly to bring about thedesired relief and intaglio efiects which I wish to appear and to bepresent in the final printing plates. To do this I prefer to proceed asfollows: I first carefully cover all area which is to print in thedarkest shades or tints, as well also as the mar gins. and face side ofthe plate, with a suitable acidproof covering or resist, leaving exposedfor etching all of the medium tone areas and lighter tone areas andblank areas. I now etch these exposed areas, preferably by putting theplate in a bath of acid and I permit the etching to continue only untilthe metal has been bitten away properly to produce the desired mediumtones or shades, as will hereinafter appear, and then wash off the acid.I new cover the medium tone areas, leaving the lighter shade areas andthe blank areas only exposed, and again etch as before until the platehas been reduced sufficiently for the lighter shades. In this connectionit may be noted that the carbon transfer lines have a slight resistingeffect which causes those lines which traverse the etched areas to besufficiently retained to be visible, and thus enable me to carbonoutline the several types of areas at the one first operation. However,I have found it feasible and satisfactory to outline only one type ofarea before etching the first time, then, before etching the secondtime, replacing the carbon and impression sheet and out lining thesecond type of areas, and so on. The steps of washing to arrest etching,covering with resist so as to leave only the blank areas or stilllighter shades, follow, until I finally have the back of the plateprovided with the desired contour. I prefer to finish up by tooling orgouging out around the extreme edges of the picture; such tooling beingcomparatively slight, but sufficient to permit the face of the plate totake a very slight set-back under its subsequent treatment and whicheffectually precludes undue impact of the inking roller and over-inkingalong such lines. I also tool out more pro nouncedly wherever I wish toproduce a vignette effect.

I furthermore tool in a special manner the somewhat abrupt steps orshoulders produced by the successive etchings, 2'. 6., between differenttones, except as to those locations where sharp contrast is desiredinstead of a soft blending or merging effect. To explain: I employ aflat chisel-edged tool or scraper by means of which I bevel off theshoulders or steps referred to, so that one bevel or depth of etchingmerges into the next by an incline.

I may effect the successive steps of etching in a way which is in acertain sense the reverse of that 'just described. That is to say, Imay, after having outlined the selected areas, cover all areas exceptthose which are to be etched deepest, then perform the first etching,then remove the resist from so much of the protected surface asrepresents the areas which are to be etched next to the deepest, andagain etch over the so enlarged area, and so on until all areas havebeen etched.

Coming now to the second branch of the process, and assuming I wish toprint di rectly from it, I take the prepared plate, put it in a suitablehydraulic or other high power press and, having placed the back of theplate against a suitable flat back support, apply pressure to the front,preferably through a yielding matrix or sheet lead, and sufficient toforce back the etched areas on the back of the plate into contact withthe back support. That is to say, I apply such force in such way as tore-shape the plate and impart to its back a substantially flat surface,disregarding, of course, the minor irregularities and minor routed outareas. I-Ieat applied in conjunction with the pressure facilitates there-shaping of the plate. This re-forming of the plate, of course, leavesthe surface with an uneven contour and with depressions wherever theplate has been thinned; the depth of the depression correspondingsubstantially to the depth of the etching at the back. The plate is nowremoved from the press and is in readiness for printing. But if I wishto use it as a master plate for the making of electrotypes, stereotypes,lead molds or other reproductions, I can very well dispense with thespecial step of re-shaping the plate by pressing, as above described,because it will receive an equivalent re-shaping in the act of makingthe lead mold therefrom, Which is afterward used for the electrotypes.That value of the make-ready treatment, even though the master plateshould be somewhat resilient and therefore spring back somewhat towardits original form after the pressure is removed.

i/Vhatever process of reproducing the final printing plates from theoriginal be followed, it will be obvious that the face of the printingplate will have the make-ready contour which has been imparted to theoriginal in the manner hereinbefore described. Accordingly such finalprinting plates are in condition for printing and embody the desiredmake-ready characteristics, without further treatment or specialmounting in the press.

An important characteristic of my process is that the printing platesproduced from the master plate are of uniform metal texture throughoutand hence have no tendency to lose value or change form under heavypressure or long working. This is in contradistinction from those plateswhich have been molded in one shape and afterward reshaped mechanicallyby pressure.

The step hereinbefore described of applying the working lay-out to theback of the plate preparatory to etching may be effected in a simple andsomewhat different manner as follows:

After having taken an impression or print from the face of the plate onsuitable paper, and with a liberal application of ink, I transfer theimpression from the paper to a second sheet by simply placing the twoace to face and putting them under pressure, so that the impression ofthe first offsets to the second. I then take the second sheet and applyits impression face directly to the back of the printing plate to beetched and by suitable pressure transfer the impression to the plate.The sheet being now removed, the impression appears clearly on the backof the plate.

I prefer to then proceed as follows: I first cover the area or areaswhich are to be held and not etched at all with a shellac or othersuitable varnish resist which will not be affected by either acid orbezin, which is used later to remove the ink mark. I next proceed toetch over the entire uncovered area, giving the plate only a very slightbite, just sufficient to etch in the metal. a clearly visible picture ofthe impression, with the exception, of course, of the protected areas. Inow clean off the ink impression with ben zin or other suitable solventfrom all unprotected areas, and then proceed to etch by stepssubstantially as previously described.

This method of transferring by ink impression has pronounced advantageswhere the subject contains much detail and the areas to be. differentlytreated. are many and small.

' made in the usual way, the first step is to carefully protect itsfront face with a per fect resist so that in the subsequent handling itwill be neither marred nor etched. The

working lay-out having been properly transferred to the clean back ofthe plate, as hereinbefore described, I proceed to etch as fol lows:

Referring to-Fig. 2, all areas of the back plate which are not to beetched at all, and which appear in white, are'first covered with asuitable acid resist, these areasbeing designated O. The first etchingstep is then performed over the unprotected areas, these being all ofthe shaded parts OfSitld- Fig. 2. The plate is then: washed (not,however, removing any of the resist) and those areas which are to beprinted next to the darkest shade or tone are covered with resist; theseareas being shaded with the horizontal lines only and designated 1. Thesecond etching step is then performed to further deepen the exposedareas, the plate washed, and; the parts which have received the twoetchings and are to receive no more covered with resist; these partsbeing marked 2 in -the-drawing, and the third, which in this mstance isthe final, step of etching formed to produce the extreme high lighttones. These latter parts are those which are covered with three linesof shading and are designated 3 in the drawing.

The back of plate is now entirely cleaned off, in readiness for tooling.The outlining of the picture, as hereinbefore described, is indicated at4:, and, as shown in the several views, is comparatively narrow. Anexample of gouging out to produce a vignett-ing effect is shown at 5,which tooling, as may be seen by reference to the Fig. 1-, causes thetone lines orshading'to disappear without any distinct break whatever.The beveling off or reducing of the steps or angles where differenttones are to blend into each other softly is accomplished by the use ofa flat graver or scraper; examples of this work being indicated at theparts marked 6. As will be seen more clearly in the sectional figures,the use of the tool forms an incline between the two surfaces ing of theseveral desired effects in treating" the plate in accordance with mymethod;-

raemes It will-be noted that the-etching out of the back of the plate bystages and to varying depths as described is characterized in that eachetched surface, no matter how shallow or lightly it be etched, isnevertheless carried back as a depressed surface, as distinguished froman etching through the inter stices of a partially screenedsurface, suchfor example as is produced in the original etching of the face of theplate through the gelatin resist. The importance of this distinction isthat inasmuch as the etching at forth, except in so'faras they are madethe subject of specific limitation in the claims.

I claimas my invention:

1. The improvement in the art of imparting make-ready character toplates, which embraces taking an impression from the face side of theplate, determining by inspection thoseareas which need tobe depressed inthe face of the plate, utilizing said impression as a working guide andthereby separating the back of the plate into selected areas, inregister with those determined by inspection, then converting the backof the plate into differently elevated surfaces by successively exposingunprotected areas to the action of an etching'fiuid and protecting otherareas by suitable resist, and finally, in effect, transferring the lowerareas at the back of the plate to the front face of the plate bypressing the varying areas at said back surface into substantially thesame plane.

2. The improvement in the art of imparting make-ready character toplates, which embraces taking an impression from the face side of theplate, determining by inspection those areas which need to be depressedin the face of the plate, utilizing said impression as a working guideand thereby separating the back of the plate into selected areas, inregister with those determined by inspection, then converting the backof the plate into differently elevated surfaces by successively exposingunprotected areas to the actlon of an etching fluid and protecting otherareas by suitable resist, reducing the steps or angular projectionsbetween selected pertions of adjoining areas, and finally, in effect,transferring the lower areas at the back of the plate-to the front faceof the plate by pressing the varying areas at said back surintosubstantially the 3. The improvement in the art of imparting make-readycharacter to plates, Which embraces taking an impression from the faceside of the plate, determining by inspection those areas Which need tobe depressed in the face of the plate, utilizing said impression as aWorking guide and thereby separating the back of the plate into selectedareas, in register With those determined by inspection, then convertingthe back of the plate into differently elevated surfaces by successivelyexposing unprotected areas to the action of an etching fluid andprotecting other areas by suitable resist, reducing the steps or angularprojections between selected portions of adjoining areas, outliningselected portions of boundaries of selected areas by re cessing the backof the plate, and finally, in effect, transferring the lower areas atthe back of the plate to the front face of the plate by pressing thevarying areas at said back surface into substantially the same plane.

ALBERT R. BOURGES.

-Witnesses ALBERT H. MCQUILKIN, AlBER'r I-I. GRAVES.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. 0.

